Weather in San Francisco in September 2025
- September is usually the hottest month of the year in San Francisco;
Average weather
Average temperature in San Francisco in September
Going from a maximum of +77°F during the day to a minimum of +55°F during the night, the temperature in September averages around +72°F.
The average maximum temperature goes down 8% by the end of the month, compared with the beginning of the month, from +70°F to +68°F.
Is San Francisco warm or cold in September?
San Francisco is typically warm in September.
Maximum temperatures go up compared to the previous month from +75°F to +75°F. The minimum temperature also goes up from +57°F to +57°F.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is the hottest month in San Francisco, here is the comparison with other months:
Water temperature in San Francisco in September
Water in San Francisco in September is Cold. It varies from +55°F to +59°F, with an average of +57°F. The air temperature averaging +75°F is higher than the water temperature.
The water temperature in September is one of the warmest of the entire year:
Can you swim in San Francisco in September?
Climate in San Francisco in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +75°F | +75°F | +72°F | ||||
| Min. temperature | ||||||
| +50°F | +48°F | +43°F | ||||
| Max. temperature | ||||||
| +93°F | +99°F | +95°F | ||||
| Rainfall | ||||||
| 1 mm | 4 mm | 29 mm | ||||
| Wind | ||||||
| 2 m/s | 2 m/s | 2 m/s | ||||
| Avg. water temperature | ||||||
| +56°F | +57°F | +57°F | ||||
| Humidity | ||||||
| 83% | 81% | 79% | ||||
| Air pressure | ||||||
| 1013 HPa | 1012 HPa | 1014 HPa | ||||
| Sunny days | ||||||
| 6 | 9 | 10 | ||||
| Cloudy days | ||||||
| 24 | 19 | 16 | ||||
| Rainy days | ||||||
| 0 | 2 | 5 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September weather is still as good as in August. The temperature levels stay the same in the area of +75°F for average maximum temperature during the day. Prepare for more rain. Average rainfall goes from 1 mm to 4 mm. It feels drier, as humidity decreases from 83% to 81%. The average wind speed doesn’t change much during September, staying around 2 m/s. The good news is there are likely to be more sunny days in September, from 6 to 9.
October brings much the same weather, it remains good.
Wind
The average wind speed is 1 m/s getting up to 2 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in San Francisco is gradually decreasing during September, going from 2 m/s to 1 m/s over the course of the month.
Rain
How was the weather last September in San Francisco?
Climate Change Over the Years
The climate in San Francisco in September has not changed that much over the last 43 years.
The average temperature was the lowest in 1982 (+65°F) and the highest in 2014 (+70°F). The driest year was 2013 with only 127 mm of rainfall, and the wettest year was 1983 with 1162 mm.
FAQ
Is September a good time to visit San Francisco?
Can you sunbathe in San Francisco in September?
Can you swim in San Francisco in September?
Is San Francisco rainy in September?
Is it sunny in San Francisco in September?
Other cities in USA
Monthly weather in San Francisco
Source of the data
For this page, we’ve looked at the typical weather in San Francisco, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.